absorbent has 2 distinct synonyms spread across 2 of its 2 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its one recorded opposite is nonabsorbent.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
a material having capacity or tendency to absorb another substance
having power or capacity or tendency to absorb or soak up something (liquids or energy etc.)
“as absorbent as a sponge”
Synonyms, antonyms and the broader and narrower relations for absorbent come from Princeton University’s WordNet. Full sources and licences.